At least 70,000 Italian workers, and thousands more from across Europe, will take to the streets of Rome today as European heads of government gather to open their conference to draw up a new EU constitution. The demonstration, called by the European TUC, has been triggered by two factors. One is peculiar to Italy. Silvio Berlusconi, the prime minister, has offended even the most moderate Italian trade unions with his cavalier and tacky approach to the serious question of pensions. It's not only the Germans, the judges, and women who feature in Berlusconi's wild blasts of invective. Unions are also subjected to abuse for sticking up for a decent pensions system. So incensed are they that the Italian unions will follow up today's protest with a general strike on October 24.

The original reason for the demonstration, however, transcends the Italian situation. It is not just Berlusconi and the political right who are on the march against trade unions. Even some left-leaning governments and socialist parties have lost faith in the postwar settlement in western Europe. The mood is that welfare states are too expensive, that public services are more efficiently delivered by applying a stiff dose of the private sector and that trade union influence should be weakened, not strengthened.

One reason, above all others, has caused the change. This is the high level of unemployment in the EU, especially in Germany, France and Italy, compared with the less regulated, less union-friendly environment of Britain - and even more so, the US. We are up now against a crude piece of political dogma: regulated labour markets and strong unions equal unemployment.

The fact that there are higher living standards and productivity in Germany, France and Italy than in Britain is somehow forgotten, as are the higher rates of capital and human investment which underpin the excellent productivity figures. No one thinks of the balance of payments, with the UK topping the EU deficit league table. No one mentions public infrastructure, where Britain struggles to reach EU average standards, never mind the best. And everyone ignores successful, but often relatively small, countries with low unemployment and high equality, which practise social partnership.

The harsh political truth is that social dialogue is out of fashion. In the world of political chic, social dialogue is so "yesterday".

So the fightback starts in Rome today. The new EU constitution could be as far reaching as the original Treaty of Rome in 1957 which established the common market. The draft actually includes social dialogue and full employment as founding principles for the new Europe. But some governments are likely to attack these provisions. There is no sign that the Blair government will do so - yet - but worryingly, it has blocked specific moves to extend the scope of determining social policy by qualified majority voting.

More specifically, we have a Labour government leading moves to block a string of new measures which would protect highly exposed, mainly female, temporary agency workers. These would remove in Britain the "freedom" to work excessive hours - a freedom abused by many employers - and would strengthen the ability of European works councils to hold large companies to proper account.

Behind these current agenda questions lurk deeper threats. There is a concerted employer attack on the German systems of codetermination, sectoral collective bargaining and strong works councils. The employers know that these stand in the way of Germany and Europe following the Anglo-American way of companies existing primarily to boost returns to shareholders.

This is the key ideological struggle facing the European left at the moment. Do we tolerate rising inequality, growing corporate power and the re-emergence of the superrich? Or do we strengthen the checks and balances of the labour movement through strong trade unions, effective social dialogue and new workers' rights.

For working people, the European adventure cannot be one which is feeble on worker rights and collective bargaining, welfare states and public services. If it is, the result will be an ebbing of any popular support for the European project. We will never build a stronger Europe on a weaker social platform.

· John Monks is general secretary of the European Trade Union Confederation and former general secretary of the TUC